Because they’re like wasps, just exist to mess shit up.

But really I think it’s mostly because they aren’t meant to kill their “intended” host. Like viruses that exist in a specific species won’t kill that species, but when it crosses to a different one that organism can’t fend it off as well and ends up succumbing to it.

It’s difficult to comprehend consciousness and willpower. So we define things we don’t understand with concepts that are more fluid subjective.

A “soul” is more than likely just a method that we have developed to understand individuality and the “self”. But like most things, the more educated you are the less you need to rely on faith and religion.